diff --git a/tests/phpunit/includes/install.php b/tests/phpunit/includes/install.php
index 82d53226a3..7081302d68 100644
--- a/tests/phpunit/includes/install.php
+++ b/tests/phpunit/includes/install.php
@@ -9,7 +9,6 @@ error_reporting( E_ALL & ~E_DEPRECATED & ~E_STRICT );
 $config_file_path = $argv[1];
 $multisite = ! empty( $argv[2] );
 
-define( 'WP_INSTALLING', true );
 require_once $config_file_path;
 require_once dirname( __FILE__ ) . '/functions.php';
 
diff --git a/tests/phpunit/tests/option/transient.php b/tests/phpunit/tests/option/transient.php
index 57a4a87682..63c4b01080 100644
--- a/tests/phpunit/tests/option/transient.php
+++ b/tests/phpunit/tests/option/transient.php
@@ -38,6 +38,10 @@ class Tests_Option_Transient extends WP_UnitTestCase {
 	 * @ticket 22807
 	 */
 	function test_transient_data_with_timeout() {
+		if ( is_multisite() ) {
+			$this->markTestSkipped( 'Not testable in MS: wpmu_create_blog() defines WP_INSTALLING.' );
+		}
+
 		$key = rand_str();
 		$value = rand_str();
 
@@ -59,6 +63,10 @@ class Tests_Option_Transient extends WP_UnitTestCase {
 	 * @ticket 22807
 	 */
 	function test_transient_add_timeout() {
+		if ( is_multisite() ) {
+			$this->markTestSkipped( 'Not testable in MS: wpmu_create_blog() defines WP_INSTALLING.' );
+		}
+
 		$key = rand_str();
 		$value = rand_str();
 		$value2 = rand_str();